Division of Environmental and Community Health

Maine Center for Disease Control & Prevention

A Division of the Maine Department of Health and Human Services

DHHSMeCDCEnvironmental and Community HealthDrinking WaterPublic Water SystemsTreatment


Treatment systems are an important part of delivering safe drinking water for many public water systems throughout the State. However, treatment only works when the proper chemicals are used in the right amounts and treatment is maintained and monitored. Failure to regularly and effectively maintain and monitor your treatment system puts the health of your customers as risk.

Addition, Removal, or Changes to Treatment

Changes in treatment processes which involve the addition or deletion of any chemicals require prior approval by the DWP. No new construction, addition, or alteration involving the source, treatment, or storage of water in any system shall be commenced until the plans and specifications have been submitted to and approved in writing by the DWP. If you wish to add, remove, or make changes to a treatment system, you should contact your field inspector or compliance officer and allow 30 days for approval.

See the Treatment Review and Approval Process (PDF) for information on the treatment approval process.

When requesting approval of a treatment modification, addition, or removal at a public water system, please complete the Drinking Water System Change Application (PDF) and provide applicable information as requested.

For more detailed information, you can also read the entire Drinking Water Treatment Review Policy and Procedure.

treatment chemicals

Chemicals and Products Used in Treatment

All chemicals used for treating drinking water must be certified to NSF/ANSI Standard 60 and all products that come in contact with drinking water (tanks, piping, fittings, etc) must be certified to NSF/ANSI Standard 61. There are a few exemptions that the Rules allow (consult the DWP for details), but generally, anything added to, or coming in contact with water, needs to be certified to these Standards. This requirement ensures that only products that have been tested and certified to be safe are used.

Drinking Water Chemicals and Additives: Quality Assurance (PDF)

Guidelines for Determining How Much Clorox® Concentrated to Use in Continuous Chlorination Systems vs. Clorox® Ultra and Clorox® Regular (PDF)

Approved Off-the-Shelf Bleach Products for the Disinfection of Potable Water (PDF)

Agencies that certify to Standard 60 and 61 include NSF International (NSF), Underwriters Laboratories (UL), and Water Quality Association (WQA). The easiest way to ensure compliance is finding a label on the product or package. However, not all chemicals are labeled as certified even if they have the certification. In these cases, it is necessary to do further investigation. This may include reviewing documentation that came with the product shipment, such as a packing slip or bill of lading, looking up the product online with the certifying agencies, or even contacting the manufacturer. You should then be prepared to provide proof that the products you are using in your treatment system (and throughout the rest of your water system) are certified.

Monthly Operating Reports

All public water systems that add a chemical(s) to their water must submit a Monthly Operating Report (MOR) to DWP. MORs help track the amount of chemical used, daily production of the water system, and the amount of chemical (residual) present in the distribution system. These measurements ensure that the treatment system is operating properly and providing protection in the drinking water supply.

It is important to remember that for those water systems required to have a Designated Operator (DO), the DO must sign every MOR before it is submitted. For those MORs submitted electronically, the MOR is considered signed by the DO if the MOR is submitted directly by the DO through e-mail.

Also note that all MORs must be submitted by the 10th of the month following the month being reported on the MOR.

Cross Connections and Bypasses

While cross connections within the entire water system should be avoided whenever possible, or properly protected when they can't, it is especially important to pay attention to cross connections within the treatment system. Cross connections that are not properly protected can result in serious and dangerous consequences of adding too much of a chemical to the system. Make-up water lines (or feed lines) should have either an air gap or a proper testable backflow prevention device installed. Hoses should never be kept attached to the feed lines or spigots in the treatment system. Remember, a closed valve is NOT a backflow prevention device.

Additionally, a bypass cannot be installed on any treatment systems that are required by the DWP. The potential for operating a valve incorrectly, or even a leaking valve, can result in contaminated water entering the distribution system, posing a risk to the safety of the water for your customers.

Standard Operating Procedures (SOPs) and Maintenance

Written Standard Operating Procedures (SOPs) are important and valuable for all operations in every water system to ensure consistency, efficiency, best practices, and continued operations during emergencies or personnel changes. Written SOPs that outline specific instructions and procedures for operating, maintaining, checking, and monitoring treatment systems are particularly important. Every treatment system process should be clearly documented and outlined in a SOP. This enables operations to remain consistent no matter which staff are on duty and also helps to serve as a resource during emergencies when an operator, or person who usually oversees the treatment system, is absent.

Along with a written SOP, a maintenance log should be recorded and kept onsite for all treatment systems to keep track of when the treatment system is serviced or changes are made. Essential spare parts should be onsite or immediately available, such as a working spare chemical feed pump. Being prepared for an emergency can help save time, money and ensure you are always able to provide safe drinking water to your customers.

Treatment Failures

If your treatment system fails or malfunctions, you must take immediate action. For treatment failures of disinfection systems, such as continuous chlorination (PDF) or UV systems (PDF), a Boil Water Order will be necessary. When other types of treatment fail such as an Arsenic Removal or a Corrosion Control treatment system, the failure may cause unsafe levels of contaminants to be present in the drinking water and may cause an immediate health risk to anyone who drinks the water. In such cases, a Do Not Drink Order or a Do Not Use Order may be necessary in order to protect the health and safety of your water system's consumers. With any treatment failure, call the DWP immediately at 287-2070 or after hours at 557-4214.

Continuous Chlorination Disinfection System Guidance Documents

Links to Professional Services

(Please note that this only a partial list, and is not an official endorsement of any company or professional. Services and prices may vary. To be included as a resource, please contact the Drinking Water Program at 207-287-2070)

Additional Resources